How to run cmd.exe under the 'system' user profile and check its folders

You have to use PSExec from the PSTools utilities

Windows 32 bit:

Windows PowerShell
    Copyright (C) 2009 Microsoft Corporation. All rights reserved.

   PS C:\Windows\system32> .\psexec -s \\localhost cmd
    PsExec v1.98 - Execute processes remotely
    Copyright (C) 2001-2010 Mark Russinovich
    Sysinternals - www.sysinternals.com


    Microsoft Windows [Version 6.1.7601]
    Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

    C:\Windows\system32>whoami
    nt authority\system

    C:\Windows\system32>cd %appdata%

    C:\Windows\System32\config\systemprofile\AppData\Roaming>

Windows 64 bit:

Windows PowerShell
    Copyright (C) 2009 Microsoft Corporation. All rights reserved.

   PS C:\Windows\SysWOW64> .\psexec64 -s \\localhost cmd
    PsExec v1.98 - Execute processes remotely
    Copyright (C) 2001-2010 Mark Russinovich
    Sysinternals - www.sysinternals.com


    Microsoft Windows [Version 6.1.7601]
    Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

    C:\Windows\SysWOW64>whoami
    nt authority\system

    C:\Windows\SysWOW64>cd %appdata%

    C:\Windows\SysWOW64\config\systemprofile\AppData\Roaming>